The position of an elevator car in the elevator hoistway can be measured indirectly from the rotational movement of the hoisting machine of the elevator. In this case a measuring error can arise, e.g. from elongation of the elevator ropes or from slipping of the elevator ropes on the traction sheave of the hoisting machine.
The location of an elevator car on a stopping floor can be detected with a magnetic switch fastened to the elevator car, which switch reacts to a permanent magnet disposed in the elevator hoistway in the proximity of the stopping floor. The mechanical contacts of magnetic switches are unreliable; vibration or an impact may cause failure of the contact, and mechanical contacts also oxidize easily.
Separate sensors, such as switches or ramps, are also usually disposed in the elevator hoistway, with which sensors the extreme limits of permitted movement of the elevator car in the elevator hoistway are measured.
Taking what is described above into account, there is a need to develop positioning solutions for an elevator car that are simpler and more reliable than those known in the art.